One and two dimensional (2d) barcodes are now in common use. The 2d barcode in particular has seen popular deployment in signs posted at various locations. Typically, the 2d barcode encodes a URL. A common usage is for a user with a cellphone that has a camera to take a picture of the barcode. Software on the cellphone decodes this to the URL. If the cellphone has (wireless) Internet access, it then goes out on the Internet to that address and downloads the webpage and displays it on the cellphone in a browser. Whereby the user can interact with it as a standard webpage.
A barcode is preferred over the display of the URL in human readable text, because the latter needs the mobile user to read it and type it into her cellphone browser. The small size of the cellphone screen and the awkwardness of typing letters on the cellphone make the input of the URL error prone.
Hitherto, from the granted patents and patents pending, as well as general knowledge of the state of the art, such displays of 2d barcodes are usually in permanent form, like printed on a poster or piece of paper.
Several 2d barcodes use black and white barcodes. This includes the encoding schemes of QR codes and Data Matrix. The use of black and white is for maximum contrast, and hence to minimise error rates in the decoding process.